There are several classes in java that are plural despite them not being utilities. These include DoubleSummaryStatistics and IntSummaryStatistics.java. I think the primary meaning is "Does making this class plural improve the understanding of the class or make it more readable?" DoubleSummaryStatistic would likely be non representative of the class itself. The majority of plural classes are utilities or constants. The other, are sometimes extensions of a HashMap for properties or attributes. From java.util, the following classes are plural: